The wireless local area network (WLAN) technology and construction have grown rapidly in recent years. The wireless network is the most important technology for the mobile Internet service. The wireless network is designed as an extension of the Ethernet, and is suitable for best-effort services, such as e-mail and web browsing. But as the real-time media applications, such as voice over IP (VoIP), video streaming, grow popular, a higher demand on the network efficiency is required to guarantee an acceptable quality of service (QoS).
The conventional development is mostly focusing on improving the bandwidth efficiency of a single access point. Many wireless resources management techniques are proposed. However, in a wireless network hotspot, the load balancing problems among the access points (APs) and the overall capacity are not fully discussed.
FIG. 1 shows a schematic view of a conventional wireless network hotspot system structure. As shown in FIG. 1, the wireless network hotspot system includes three parts: Internet, distributed system, and WLAN hotspot.
A wireless network hotspot includes many APs and stations (STAs), and has the following three functions. The first is the admission control unit, through which the APs can determine whether sufficient resources are available for supporting the QoS request. Many admission control techniques can achieve such a function, such as the reference admission control mechanism of IEEE802.11e specification. The second is the radio measurement and management facilities, through which the APs can request the connected STAs to measure the radio, and report the measurement to the APs. Hence, the APs can know the information of the neighboring APs. There are several radio measurement and management techniques, such as IEEE802.11k specification. The third is the fast handoff. The STAs and APs can use the fast handoff technique of IEEE802.11r specification or related techniques.
As shown in FIG. 1, the coverage areas of the APs in a wireless network hotspot usually overlaps with one another. When a wireless network STA is in the network entry stage, a plurality of APs can be detected. The STA usually selects the AP with the best received signal strength indicator (RSSI) to associate with and establish the connection. Then, the STA will occupy some AP resources, such as bandwidth and AP buffer, for service. However, this type of STA-centric network association and service request will lead to the load unbalance among the APs in the wireless network hotspot so that the bandwidth can not be effectively utilized. For wireless multimedia service, such as voice over WLAN (VoWLAN), that demands high quality service, this is an important issue.
The STAs can establish a non-QoS connection or a QoS connection with the AP. When a non-QoS connection is established, such as FTP, e-mail, wed browsing, the so-called best effort (BE) and background (BK) services, the AP does not guarantee the quality of the non-QoS services. When a QoS connection is established, such as voice (VO) or video (VI) connection, the quality of service is guaranteed by the AP. Because the AP must provide QoS guarantee, the majority of bandwidth resources of an AP is allocated to the QoS connections, for example, 80% vs. 20% allocation for QoS and non-QoS, respectively.
FIG. 2 shows a schematic view of a conventional wireless network load system. As shown in FIG. 2, an STA S3 in the network entry stage detects APs A1, A2, and selects an AP with best signal, for instance, A1, for association. When a second STA S9 tries to establish a QoS connection, such as VO or VI connection, S9 issues a QoS connection request to A1. A1 uses admission control unit to determine whether the request can be admitted. As the QoS bandwidth of A1 is fully occupied, the request from S9 cannot be admitted.
In other words, the conventional STA-centric network association mechanism may lead to load unbalance among APs, and results in poor bandwidth utilization.
U.S. Pat. No. 6,574,474 disclosed a method for the STA to select the AP association based on the AP signal strength and load condition so as to achieve load balancing in the wireless network.
U.S. Pat. No. 6,574,477 disclosed a method for load balancing two APs of a single cell. U.S. Pat. No. 6,069,871 disclosed a cellular wireless communication system for multi-carriers. When an STA requests a connection with a base station (BS), a method for searching for a neighbor BS will be provided if the requested BS does not have sufficient resource to provide the connection. The neighbor BS must have sufficient resource to provide the QoS to the requesting STA. International Publication WO 2004/004226 disclosed a method that, in a wireless network, when the bandwidth resource of an AP is below the threshold, the AP searches for a neighbor AP with sufficient bandwidth so that the bandwidth of the neighbor AP will not be below the threshold after providing the service to the STA. All these techniques are specific mechanism activated under specific condition, instead of general solution.
It is imperative to provide a load balancing technique to improve the bandwidth utilization of a wireless network system.